CPR volume exchanger valve system with safety feature and methods

ABSTRACT

A method for regulating gas flows into and out of a patient includes repetitively forcing respiratory gases out of the lungs. Respiratory gases are prevented from entering back into the lungs during a time between when respiratory gases are forced out of the lungs. Periodically, an oxygen-containing gas is supplied to the lungs.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/871,879, filed Oct. 12, 2007 which claims the benefit ofU.S. Provisional Application No. 60/912,891, filed Apr. 19, 2007, thecomplete disclosures of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

This invention relates generally to the field of cardiopulmonaryresuscitation, and in particular to techniques to increase circulationwhen performing CPR.

Despite current methods of CPR most people die after cardiac arrest. Oneof the major reasons is that blood flow to the heart and brain is verypoor with traditional manual closed chest CPR. Greater circulation ofblood during CPR will result in improved outcomes.

BRIEF SUMMARY OF THE INVENTION

In some embodiments, methods are described for regulating gas flows intoand out of a patient. According to one method, respiratory gases arerepetitively forced out of the lungs. Respiratory gases are alsoprevented from entering back into the lungs between chest compressions.Periodically, an oxygen-containing gas is supplied to the lungs toprovide ventilation.

In one particular aspect, the gases are repetitively forced out of thelungs by repetitively compressing the chest and permitting the chest torecoil a rate of about 60 to about 120 times/min. In a further aspect, alow flow and volume of oxygen is continuously supplied to the lungs.This volume of oxygen is less than the volume of respiratory gasesexpelled with successive chest compressions so that the number of timesthat the lungs are expanded with oxygen-containing gases is reduced bythe low level of continuous oxygen insufflation.

Other embodiments of this invention include methods and devices forincreasing circulation during CPR by reducing the volume of air in thelungs during chest compressions so that the thorax has more space topermit more blood flow into the heart with each chest compression/chestrecoil cycle. Such embodiments include ways to compress the chest andallow it to recoil. During each compression, air is pushed out of thelungs through a one way valve. Every time the chest wall recoilsfollowing a compression, air (or respiratory gases) from outside thepatient is prevented from passively entering the lungs. With sequentialcompressions, less and less air remains in the thorax. This gradualextrusion of respiratory gases from the lungs with each chestcompression results in more space within the thorax (lungs, bloodvessels, and heart) to be filled with blood. With more blood in thechest and less air, each time the chest is compressed more blood isejected from the heart. After some number of compressions, such asbetween about 12 and about 30 (depending upon how many people areperforming CPR and if the airway is secured with a face mask versus andendotracheal tube or equivalent), air is allowed to actively enter thelungs either by the delivery of a positive pressure breath from aventilation source or by negative pressure ventilation (e.g. an ironlung or equivalent).

One advantage of such techniques is that during the chest recoil,intracranial pressures are decreased more rapidly and to a lower value,thereby further increasing the duration and magnitude of cerebralperfusion pressure.

In one particular aspect, the volume of respiratory gas expelled over aseries of chest compression/recoil cycles is in the range from about 1to about 15 cc/kg. Also, the volume of respiratory gases expelled fromthe chest may be expelled against a low level of fixed or variableresistance that is in the range from about 0 cm H2O to about 10 cm H2O.

In a further embodiment, the invention provides an exemplary device toaugment circulation during the performance of cardiopulmonaryresuscitation in a patient in cardiac arrest. The device comprises ahousing having a rescuer port and a patient port. A valve system isdisposed in the housing. Further, the housing and the valve system areconfigured such that a volume of respiratory gas expelled from the lungsduring each chest compression enters the housing through the patientport, passes through the valve system and exits the rescuer port. Also,when the chest wall recoils, oxygen containing gases are prevented fromentering the lungs through the patient port by the valve system. Aventilation source may also be used to inject an oxygen-containing gasinto the housing which passes through the valve system, through thepatient port and to the patient to periodically expand the lungs withthe oxygen-containing gases.

The valve system may be constructed using a variety of valves, such ascheck valves, spring valves, duck valves, electronically-controlledvalves and the like. As another example, a pair of one way valves may beused that are separately configured to open with opposite gas flowspassing through the housing. Also, a variety of ventilation sources maybe used, such as mouth-to-mouth ventilation, a mouth-mask, aresuscitator bag, an automatic ventilator, a semi-automatic ventilator,a body cuirass, an iron-lung device and the like. In another aspect, thevalve system may include a means to impede the exodus of respiratorygases from the lungs with a fixed or variable resistance that is in therange from about 0 cm H₂O to about 10 cm H₂O.

In one particular arrangement, at least one physiological sensor may beused to measure one or more physiological parameters. Such sensors mayinclude electrocardiogram signal sensors, impedance sensors to detectair/blood ratio in the thorax, and the like. Also, a communicationsystem may be employed to permit signals from the physiologicalsensor(s) to be transmitted to a CPR device used during resuscitation toprovide various types of feedback. This can include how to perform CPR,an optimal time to actively inflate the lungs with respiratory gases, anoptimal time to defibrillate, and the like. Further, timing lights maybe employed to assist a rescuer in performing CPR, such as when toprovide chest compressions.

In a further aspect, a supply system may be used to deliver a low flowand volume of continuous oxygen into the lungs which is less than thevolume of respiratory gases expelled with successive chest compressions.In this way, the number of times that the lungs are expanded withoxygen-containing gases is reduced by the low level of continuous oxygeninsufflation.

In still another embodiment, the invention provides a device to augmentcirculation during the performance of cardiopulmonary resuscitation in apatient in cardiac arrest. The device comprises a housing having arescuer port and a patient port. Means are provided for regulating gasflows through the housing such that a volume of respiratory gas expelledfrom the lungs during each chest compression enters the housing throughthe patient port and exits the rescuer port. Also, when the chest wallrecoils, oxygen containing gases are prevented from entering the lungsthrough the patient port. A ventilation source is employed to inject anoxygen-containing gas into the housing and to pass through the patientport and to the patient to periodically expand the lungs with theoxygen-containing gases.

In one aspect, the means for regulating gas flows comprises a pair ofone way valves that are separately configured to open with opposite gasflows through the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph illustrating lung volume while performing CPR whenapplying techniques according to the invention.

FIG. 2A schematically illustrates expired respiratory gases passingthrough a valve system during a chest compression according to theinvention, along with a control system and a sensor.

FIG. 2B schematically illustrates how respiratory gases are preventedfrom passing through the valve system and into the lungs during chestrecoil or chest decompression according to the invention.

FIG. 2C schematically illustrates the injection of an oxygen-containinggas through the valve system to provide patient ventilation according tothe invention.

FIG. 2D schematically illustrates the passage of respiratory gasesthrough a safety check valve if the patient inspires according to theinvention.

FIG. 3A illustrates one embodiment of a valve system according to theinvention.

FIG. 3B is a cross sectional side view of the valve system of FIG. 3Aillustrating gas flows with patient exhalation (such as during a chestcompression), along with a control system and a sensor.

FIG. 3C is a cross sectional side view of the valve system of FIG. 3Aillustrating the absence of gas flow when the patient's chest recoils oris lifted.

FIG. 3D is a cross sectional side view of the valve system of FIG. 3Aillustrating gas flows when delivering an oxygen-containing gas to thepatient.

FIG. 4 is a flow chart illustrating one method for performing CPRaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Multiple methods of chest compression may be used when performing CPR inpatients in cardiac arrest. In this life-threatening situation, theheart is not capable of circulating blood so non-invasive external meansare used to assist in the circulation of blood to the vital organsincluding the heart, lungs, and brain. The methods and devices that maybe used to circulate blood during cardiac arrest include manual closedchest CPR, active compression decompression (ACD) CPR where thepatient's chest is actively pulled upward (including by use of amechanical assistance device that is adhered to the chest) to achievecomplete chest wall recoil, mechanical CPR with manual or automateddevices that compress the chest and either allow the chest to recoilpassively or actively, and devices that compress the chest wall and thenfunction like an iron lung and actively expand the thoracic cage. Someof these approaches and devices only compress the anterior aspect of thechest such as the sternum while other approaches and devices compressall or part of the thorax circumferentially. Some approaches and devicesalso compress the thorax and abdomen in an alternating sequence. Someapproaches also involve compressing the lower extremities to enhancevenous blood flow back to the heart and augment arterial pressure sothat more blood goes to the brain. Some approaches also involvecompressing the back, with the patient lying on his/her stomach. Somedevices include both non-invasive methods and devices outlined abovethat are coupled with invasive devices, such as an intra-aortic balloon,and devices to simultaneously cool the patient

Because the cardiac valves remain essentially intact during CPR, bloodis pushed out of the heart into the aorta during the chest compressionphase of CPR. When the chest wall recoils, blood from extrathoraciccompartments (e.g. the abdomen, upper limbs, and head) enters thethorax, specifically the heart and lungs. Without the next chestcompression, the blood would pool in the heart and lungs during cardiacarrest as there is insufficient intrinsic cardiac pump activity topromote forward blood flow. Thus, chest compressions are an essentialpart of CPR.

During the compression phase air is pushed out of the thorax and intothe atmosphere via the trachea and airways. During the decompressionphase it passively returns back into the thorax via the same airwaysystem. As such, respiratory gases move out of and back into the thorax.With each compression the pressure within the chest is nearlyinstantaneously transmitted to the heart and also to the brain via thespinal column and via vascular connections. Thus, with each externalchest compression pressure in the thorax and within all of the organs inthe thorax is increased. Application of the methods and devicesdescribed in this application, in conjunction with any of the methods ofCPR noted above, result in less and less air in the thorax, making roomfor more and more blood to return to the heart during the chest wallrecoil phase. This increases circulation to the coronary arteries andlowers intracranial pressure during the chest wall decompression phaseand with each subsequent compression increases blood flow to the vitalorgans, especially the brain. Since the delivery of oxygen is animportant aspect of CPR, periodically a positive pressure ventilationneeds to be delivered to inflate the lungs and provide oxygen. The lungscan also be inflated by periodic negative pressure ventilation with, forexample, an iron lung or chest cuirass device. With both positive andnegative pressure ventilation, typically a patient receives a tidalvolume of about 500-1000 cc during each active ventilation (positivepressure ventilation). Thus, with the practice of this invention, anequal volume of respiratory gas is extruded from lungs over the courseof several compressions so that after about 2 to 6 compressions thedelivered volume has been removed from the thorax and its space can bereplaced by blood that refills the thoracic space. This exchange is madepossible by the fact that pressures within the thorax are transducedfrom one organ to another nearly instantaneously. This pressure transferoccurs between different thoracic compartments, for example the lungsand the right heart, very rapidly, especially between organs in thethorax with a high degree of compliance. For example, positive pressuresare transferred during the compression phase from the lungs to the rightheart, and as such right heart pressures are markedly increased witheach chest compression. The increase in pressure within the lungs istransferred to the heart, propelling blood within the heart chambers ina forward direction along the course from right atrium to rightventricle to pulmonary artery pulmonary vein, left ventricle, and outthe aorta. The inverse is also true, with chest wall recoil the negativepressures are transmitted throughout the thorax, including the spinalcord. This pulls blood into the heart and lungs from outside the thorax.The decreases in pressures within the thorax are augmented by themethods and devices described herein. The more gas that is pushed out ofthe lungs with each compression and not allowed back in, the more spaceis made available for blood to flow into the organs within the thoraxeach time the chest wall recoils. The volume of respiratory gas that isexpelled over a series of chest compression/recoil cycles may be about 5to about 15 cc/kg. It would typically be expelled after about 2 to 6compression/recoil cycles. The volume of air expelled from the chestcould be expelled against a low level of fixed or variable resistance,typically in the range from about 0 cm H₂O to about 10 cm H₂O. Thiscould be adjustable and could be provided by a valving system or othermeans having a low flow of positive pressure gases, such as oxygen. Thisprocess can be further augmented by active compressions and activedecompressions. This process can also be further augmented by activelyextracting a volume of respiratory gases between positive pressurebreaths, creating even more space in the thorax to be filled with bloodwith each decompression phase of CPR to prime the heart for the nextcompression.

Periodically the lungs need to be inflated so that the pulmonaryvascular resistance (blood pressure in the blood vessels in the lungs)does not get too high (which happens when the lungs are empty andcollapse) which would limit blood flow through the lungs. Periodicinflation of the lungs also provides oxygen and helps to clear carbondioxide. This process is depicted graphically in FIG. 1. The left-Y axisshows the volume of respiratory gas in the lungs in liters and the Xaxis shows time in seconds. At point A, a positive pressure breath isdelivered. Down and up arrows show when chest compression anddecompression (in this example passive chest wall recoil) occurs.Changes in the volumes of respiratory gases in the lungs when using theinvention are shown by the solid line. With each chest compression airis pushed out of the lungs, and not allowed back into the lungs becauseof the valve system. This results in a progressive decrease inrespiratory gases within the lungs. The shaded area, labeled B, is thevolume of respiratory gas that is expelled from the lungs with eachchest compression. The total volume, shown by B, creates space that isfilled by more blood returning to the heart and lungs during thedecompression phase whenever a positive pressure is not being applied tothe thorax by chest compressions. By contrast, changes in the volumes ofrespiratory gases in the lungs without the invention are shown by thehashed line. Each compression and chest wall recoil cycle is associatedwith a slight increase and decrease in pressures in the airway asrespiratory gases move freely into and out of the lungs with eachdecompression and compression cycle.

A variety of valves may be coupled to the patient's airway to permitrespiratory gases to escape from the lungs during chest compressions,while permitting periodic ventilation. One type of valve could be aone-way valve, typically used in combination with another one-way valvethat opens in the opposite direction and which is biased in the closedposition so that gases cannot enter the lungs during chest recoil orchest decompression. Another valve system that may be used is describedin U.S. Pat. Nos. 5,692,498; 6,062,219; 6,526,973; and 6,604,523,incorporated herein by reference. With such valves, the thresholdcracking pressure could be set high enough so that respiratory gaseswere always prevented from entering into the lungs until activelyventilated.

Airflow into and out of the chest through one embodiment of theinvention is shown schematically in FIGS. 2A-C. In FIG. 2A, a valvesystem 10 is schematically illustrated. Valve system 10 has a patientport 12 which interfaces with the patient's airway and a rescuer port 14used by a rescuer to provide ventilation to the patient. When the chestis compressed (as illustrated by the hands pressing down on the chestwall), respiratory gases flow from the patient through the valve system10 as shown by the arrow. In so doing, the respiratory gases pass intoroom air with minimal or no resistance from valve system 10. In FIG. 2B,the chest wall recoils during the decompression phase as the rescuer'shands are lifted (or the chest is actively lifted upward). Now, valvesystem 10 prevents respiratory gases from entering the patient. In FIG.2C a positive pressure ventilation is delivered through rescuer port 14wherein passes through valve system 109 and out patient port 12 where ispasses to the patient's lungs. As such, with each chest compression,more and more gases are forced out of the lungs. This is because duringdecompression, gases are prevented from entering. When needed, gases canbe injected into the lungs to provide adequate ventilation.

In some cases, the patient may begin to breathe or gasp spontaneously.As shown in FIG. 2D, valve system 10 has one or more safety check valves16 to permit gases to pass through patient port 12 and into the lungs.As one example, safety check valves 16 may be set to open at about −10cm H2O. This schematic is not meant to be limiting but ratherdemonstrative of airflow through one potential embodiment of theinvention during CPR.

The invention may employ a variety of techniques to enhance circulation.For example, a device to augment circulation during the performance ofcardiopulmonary resuscitation in a patient in cardiac arrest may beconfigured to allow a volume of respiratory gas from the lungs to exitthe airway with each external chest compression but prevents oxygencontaining gases from passively reentering the lungs each time the chestwall recoils. This may be done using a valve system having a one-wayvalve and a means to periodically expand the lungs withoxygen-containing gases. Such a device may be particularly useful whenthe chest is compressed and allowed to recoil at a rate of about 60 toabout 120 times/min. Such a device may also permit a volume ofrespiratory gases to be expelled from the lungs with each compression.Such a device can be used with manual CPR, ACD CPR, manually operatedCPR devices, or automated CPR devices. With each chest wall recoil,respiratory gases are prevented from returning to the lungs by means ofa one-way valve. Over each successive chest compression/chest recoilcycle there is a successive decrease in respiratory gases within thelungs. Periodically, the lungs are actively expanded withoxygen-containing gas.

The valve system can be made of one or more check valves, spring valves,duck valves, other mechanical or electronically controlled valves andswitches. The lungs are periodically expanded by a ventilation sourcethat could include: mouth-mouth ventilation, mouth-mask, a resuscitatorbag, an automatic or semi-automatic ventilator, a body cuirass oriron-lung like device or the like. A variety of sensors could beincorporated into the system to guide the ventilation rate and/ordetermine the degree of chest compression and/or degree of chest wallrecoil including: airway pressure sensors, carbon dioxide sensors,and/or impedance sensors to detect air/blood ratio in the thorax to helpguide ventilation and compression rate.

The valve system could include a one-way valve with a means to impedeexhalation or the exodus of respiratory gases with a fixed or variableresistance. This could be in the range from about 0 to about 20 cm H₂O,and in some cases about 0 to about 10 cm H20. This may also beadjustable. In some cases such expiratory resistance helps to push bloodout of the lungs back into the left heart, and serves as a means to helpprevent buildup of blood in the lungs during CPR.

One particular embodiment of a valve system 20 is shown in FIG. 3A.Valve system 20 is constructed of a housing, which is convenientlymanufactured as an inspiration interface housing 22 and a patientinterface housing 24. A ventilation source port 26 for ventilation tothe patient is included in housing 22 while a connector port 28 isincluded in housing 24. In this way, a ventilation source may be coupledto port 26 and port 28 may be used to interface with the patient, andthe patient's airway. A valve plate 30 having a pair of one-way checkvalves 32 and 34 in between.

As shown in FIG. 3B, during chest compression, respiratory gases flowfrom the patient and pass through port 28 where the gases openexpiratory check valve 34. From there, the gases exhaust to theatmosphere through port 26. Optionally, valve 34 may be biased in theclosed position, and may open when the exiting gases exert a pressurethat is less than about 20 cm H2O.

Port 28 may be coupled to a patient interface 21, which could include afacial mask, endotracheal tube, other airway device or any of the otherinterfaces described herein. Port 26 may be coupled to a ventilationsource 23, such as a ventilator bag, ventilator, tube for performingmouth-to-mouth resuscitation, or any of the other devices describedherein.

Further, a controller 25 may be employed to control any of theelectronic equipment. Controller 25 may include a storage device, suchas memory, one or more processors and appropriate hardware and/orsoftware for performing operations under the direction of the processor.For example, if ventilation source 23 were a ventilator, controller 25may be employed to control operation of the ventilator. One or moresensors 27 may be coupled to controller to monitor various physiologicalparameters of the patient as described herein. Also, controller 25 couldmodify application of chest compressions and/or ventilations based onthe sensed parameters.

Controller 25 may also be coupled to one or more timing lights 29 whichcould be used to indicate to a rescuer as to when to provide chestcompressions and/or ventilations.

In FIG. 3C, the chest wall recoils. Inspiratory check valve 32 is biasedin the closed position, by use of a spring, elastomer or the like, sothat no respiratory gases are allow through inspiratory check valve 32.Valve 32 may be biased closed until a pressure in the range of about −5to about −10 mmHg is achieved. This is most likely to occur when thepatient takes a spontaneous gasp during CPR, and then airflow movesthrough the inspiratory check valve 32 to the patient through port 28.This can also occur if a rescuer ventilates the patient rapidly with alarge tidal volume rapidly through port 26 as shown in FIG. 3D.

Any of the valve systems described herein could also include or beassociated with physiological sensors, timing lights, impedance sensorsto detect air/blood ratio in the thorax, and a way to communicate with aCPR device or other apparatus used during resuscitation (e.g.defibrillator) to provide feedback in terms of how to perform CPR, theoptimal time to actively inflate the lungs with respiratory gases or theoptimal time to defibrillate.

The valve systems or associated devices could also include a way todeliver a low flow and volume of continuous oxygen into the lungs whichis less than or just equal to the total volume of the expelled volume ofrespiratory gases with chest compressions so that the number of timesthat the lungs are expanded with oxygen-rich gases is reduced by the lowlevel of continuous oxygen insufflation.

One exemplary method for controlling gas flow into and out of apatient's lungs is illustrated in FIG. 4. At step 40, cardiopulmonaryresuscitation is performed on a patient in cardiac arrest. This may beperformed by compressing the chest and allowing the chest to recoil at arate of about 60 to about 120 times/min.

For a plurality of chest recoils, respiratory gases are prevented fromreturning to the lungs such that over successive chest compression/chestrecoil cycles there is a successive decrease in respiratory gases withinthe lungs (see step 42). This allows more blood to enter the thoracicspace (the volume of respiratory gas expelled over a series of chestcompression/recoil cycles optionally being in the range from about 4 toabout 15 cc/kg). Hence, over each successive chest compression/chestrecoil cycle there is a successive decrease in respiratory gases withinthe lungs thereby allowing more blood to enter the thoracic space.

Periodically, the patient may be ventilated (see step 46), such as byperiodically actively expanding the lungs with an oxygen-containing gas.During the chest recoil phase of CPR, intracranial pressures aredecreased more rapidly and to a lower value thereby further increasingthe duration and magnitude of cerebral perfusion pressure. Optionally,the volume of respiratory gas expelled from the chest may be expelledagainst a low level of fixed or variable resistance that is in the rangefrom about 0 to about 10 cm H2O (see step 48).

The devices and methods described herein may be used with any type ofCPR technique that involves manipulation of the chest to changepressures within the thorax would benefit from this improved method ofinvention. Also, the method for providing periodic expansion of thelungs could include mouth-mouth ventilation, a resuscitator bag, anautomatic or semi-automatic ventilator, a body cuirass or iron-lung likedevice. The method could also include a way to deliver a low flow andvolume of continuous oxygen into the lungs which is less than the totalvolume of the expelled volume of respiratory gases so that the frequencyof positive pressure ventilations by an external ventilation sourcecould be reduced by the low level of continuous oxygen insufflation (seestep 50).

A variety of sensors could be used to guide the periodic ventilationrate or determine the degree of chest compression or degree of chestwall recoil. Sensors could include airway pressure sensors, timinglights, carbon dioxide sensor, electrocardiogram signal sensors, and/orimpedance sensors to detect air/blood ratio in the thorax to help guideventilation and compression rate and determine if CPR should becontinued, the optimal time and way to defibrillate, and when to stopCPR efforts because of futility.

The method could include a number of different airway adjuncts tomaintain a seal between the trachea and the ventilation source orpharynx and ventilation source or mouth and ventilation source (e.g.endotracheal tube, face mask, laryngeal mask airway, supraglotticairway, and the like). Sensors within these airways could be used toverify proper airway adjunct placement. Such sensors could include acarbon dioxide detector which could be housed in a manner that isprotected from bodily fluids.

The method could include a means to transmit the amount of respiratorygas volume delivered or expelled from the chest to a monitoring systemthat could be used as part of a closed loop circuit to maximize thenumber of compressions interspersed between active ventilations in orderto maximize circulation during CPR. Circulation during CPR could bemeasured by a variety of means including measurement of end tidal carbondioxide, the change in expired end tidal carbon dioxide levels over agiven time interval, a change in impedance within the body, and changesin other physiological parameters such as temperature.

In some embodiments, the invention provides the ability to utilize oneor more sensors that are associated with the valve systems describedherein to indirectly measure the rate and depth of chest compression.For instance, the sensors may measure the respiratory gases (alsoreferred to as “air”) delivered to the patient, the airway pressure andthe like, and then used to estimate the rate and depth of chestcompression. This provides a convenient way to measure the quality ofCPR. This may be done, for example, by comparing variations in amount ofair delivered (or airway pressure) produced by positive-pressureventilation to the air expelled (or airway pressure variations) producedduring chest compressions. This provides an easy way to monitor, analyzeand report the depth of compressions, particularly to the user in realtime. This feedback allows the user an opportunity to continuouslyadjust or change the depth of manual (or automatic) compressions toachieve a targeted depth of compressions. Also, the pressure or volumeof air generated by positive-pressure ventilation or delivered by amanual resuscitation bag can be analyzed and reported to the caregiverfor monitoring and adjustment purposes. In addition to calculationswhich report actual compression depth and breathing pressure, thefrequency and duration of both breaths and compressions can be monitoredand reported to the user. Hence, frequency of compressions andventilation can be controlled to provide a targeted frequency or rate.

As one example, measurements may be taken using one or more sensorsdisposed anywhere within valve system 20, such as within the housing orone of the valves. For example, a sensor could be disposed ininspiration interface housing 22 or in patient interface housing 24. Asanother option, the sensor could be positioned within ventilation sourceport 26, or within one-way check valves 32 or 34. Pressure or air volumemeasurements may be transmitted to a controller, such as controller 25,either wirelessly or by a wired connection. Controller 25 may beprogrammed to determine the depth of chest compressions, timing,frequency, and the like, as described above using the pressure or airvolume readings. Further, various visual and/or audio signals may beprovided to the rescuer giving feedback as to depth or compressions,rate of compressions, rate of ventilation and the like. Controller 25may be programmed to provide this feedback, such as to timing lights,computer display screens, speakers, and the like.

The invention has now been described in detail for purposes of clarityand understanding. However, it will be appreciated that certain changesand modifications may be practiced within the scope of the appendedclaims.

What is claimed is:
 1. A method to perform cardiopulmonary resuscitationin a patient in cardiac arrest, the method comprising: providing a valvesystem comprising a pressure-responsive valve that is configured to becoupled to the patient's airway; providing at least one timing lightthat is configured to help guide a rescuer in performing a desiredcompression rate when repetitively compressing the chest; providinginstructions to repetitively compress the chest and permit the chest torecoil a rate of about 60 to about 120 times/min by following a cadenceof the timing light; providing instructions as to a proper depth foreach chest compression; wherein with each compression a volume ofrespiratory gas is expelled from the lungs; wherein for a plurality ofchest recoils, respiratory gases are prevented from returning to thelungs with the valve system such that over successive chestcompression/chest recoil cycles there is a successive decrease inrespiratory gases within the lungs thereby allowing more blood to enterthe thoracic space; and providing instructions to periodically activelyexpand the lungs with an oxygen-containing gas.
 2. A method as in claim1, wherein the step of permitting the chest to recoil comprisespermitting the chest to recoil by its own resilience or by activelypulling upward on the chest to achieve complete chest wall recoil.
 3. Amethod as in claim 1, wherein during the chest recoil, intracranialpressures are decreased more rapidly and to a lower value therebyfurther increasing the duration and magnitude of cerebral perfusionpressure, and further comprising providing a pressure-responsive one wayvalve that opens to permit air to flow into the lungs through the valveif the patient begins to breathe.
 4. A method as in claim 1, wherein thevolume of respiratory gas expelled over a series of chestcompression/recoil cycles is in the range from about 1 to about 15cc/kg.
 5. A method as in claim 1, further comprising expelling thevolume of respiratory gas from the chest against a low level of fixed orvariable resistance that is in the range from about 0 to about 10 cmH2O.
 6. A method as in claim 1, further comprising providing visual oraudible instructions to a rescuer as to a desired compression orventilation rate.
 7. A method as in claim 1, further comprisingmeasuring patient gas volumes or airway pressures, and using acontroller having a memory and a computer processor to estimate the rateand depth of chest compressions by evaluating variations in the amountof gasses delivered or airway pressure produced by positive-pressureventilations to the amount of gasses expelled or airway pressuresproduced during chest compressions or chest recoil.
 8. A method as inclaim 1, wherein respiratory gases are prevented from reaching the lungsuntil about 2 to about 6 compressions have been performed.
 9. A methodto perform cardiopulmonary resuscitation in a patient in cardiac arrest,the method comprising: providing a valve system comprising apressure-responsive valve that is configured to be coupled to thepatient's airway; providing at least one sensor to sense at least oneof: ventilation rate, degree of chest compression or rate of chestcompression; providing instructions to repetitively compress the chestand permit the chest to recoil a rate of about 60 to about 120times/min; providing instructions as to a proper depth for each chestcompression; wherein with each compression a volume of respiratory gasis expelled from the lungs; wherein for a plurality of chest recoils,respiratory gases are prevented from returning to the lungs such thatover successive chest compression/chest recoil cycles there is asuccessive decrease in respiratory gases within the lungs therebyallowing more blood to enter the thoracic space; providing instructionsto periodically actively expand the lungs with an oxygen-containing gas;and wherein the sensor is configured to provide feedback to a rescuer asto whether the ventilation rate, degree of chest compression and/or rateof chest compression are proper.